A second baby girl who was found unresponsive in a Brisbane home has died in hospital overnight.
Police were called to the Sunnybank Hills home on Wednesday morning.
One of the six-week-old twins was declared dead at the scene.
The second girl was taken to hospital in a critical condition on Wednesday morning.
Police said preliminary investigations suggested the new-borns had been sleeping together throughout the night.
A report will be prepared for the coroner.
Police are not treating the deaths as suspicious.
The Red Nose charity, which aims to raise awareness of Sudden Infant Death Syndrome, issued a reminder to parents of the dangers of co-sleeping and co-bedding on Wednesday.
Co-sleeping is the practice of sharing the same surface with an infant, while co-bedding is when two babies or more share the same cot or bed.
“Red Nose is saddened to learn of the tragic death of an infant and injury to another in Queensland,” the charity said.
“Co-sleeping or sharing a sleep surface can increase the risk of death and injury, in some circumstances.
“Sleeping twins in the same cot is dangerous if one part of the body of one twin were able to accidentally cover the face of the other, causing an interference with breathing.
“There is a risk that this can happen if the infants are sleeping side-by-side.”
Police said whether the mother was co-sleeping with the two babies would form part of their ongoing investigation.